JP2009238773A - Temperature measuring method in wafer heat treatment apparatus and temperature control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature measuring method capable of precisely measuring the temperature distribution of a wafer in a wafer heat treatment apparatus. <P>SOLUTION: The method is used to measure the temperature of the wafer 30 to be heated by the wafer heat treatment apparatus 10 having an induction heating coil 18 enabling individual control of applied power and a graphite 24 having a heat region determined by the induction heat coil 18. In the method, the temperature distribution of the surface of the wafer 30 is measured by a thermography unit 60, and an average temperature per indirect heating region unit in the wafer 30 is calculated based on the measured temperature data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature measurement method in a wafer heat treatment apparatus, and a temperature control method using the temperature measurement method, and particularly suitable for performing temperature control that maintains the temperature distribution of the entire wafer to be heat treated with high accuracy. The present invention relates to a measurement method and a temperature control method.

  It is known to use induction heating as a technique for rapidly increasing the temperature of a member to be processed such as a semiconductor wafer or a liquid crystal wafer. As a technique for heating a semiconductor wafer or the like using induction heating, a semiconductor wafer is placed on a susceptor composed of a high resistance member such as graphite, and the susceptor is induction heated. According to such a technique, the semiconductor wafer is heated in a short time by receiving radiant heat or heat transferred from the susceptor that has been rapidly heated by induction heating. Based on such technology, the applicant of the present application has proposed a heat treatment technology using induction heating as disclosed in Patent Document 1.

The technique disclosed in Patent Document 1 is a technique for solving the problem of heating control by mutual induction, which is a problem that occurs when heating control is performed by arranging a plurality of induction heating coils close to each other. is there. By using this technique, it is possible to reliably control the input power for a plurality of induction heating coils arranged close to each other. And by making it possible to reliably control the input power to the induction heating coils arranged close to each other, the temperature distribution of graphite as the induction heating member is made uniform or has an arbitrary temperature gradient. In this state, it is possible to rapidly raise the temperature.
JP 2005-529475 A

  By using the technique disclosed in Patent Document 1, it is possible to arbitrarily control the temperature distribution of graphite as the induction heating member. However, when the temperature distribution control of a semiconductor wafer or the like to be processed is to be performed with high accuracy, the temperature detection accuracy for determining the amount of power to the induction heating coil, that is, the temperature distribution of the member to be processed such as a semiconductor wafer Detection accuracy becomes a problem.

  For example, conventionally, a thermocouple that is a contact-type temperature detection unit, a radiation thermometer that is a non-contact type temperature detection unit, or the like has been used as the temperature detection unit. There are the following problems.

  First, since the thermocouple cannot directly detect the temperature by contacting the member to be processed, the temperature of the induction heating member such as graphite is measured, and the temperature of the member to be processed is estimated based on this value. There is a problem of lack of accuracy and reliability.

  Next, since a radiation thermometer is spot measurement, there exists a problem that the temperature distribution of the whole to-be-processed member cannot be known. Further, the radiation thermometer has a problem that, when the spot range is widened, if the temperature gradient exists within the spot range, the reliability of the measurement value itself deteriorates.

  Due to the above problems, it has been impossible to detect the temperature of the member to be processed with high accuracy. Therefore, in the present invention, in the wafer heat treatment apparatus, a temperature measurement method capable of measuring the temperature distribution of the wafer in detail, and a temperature control method capable of realizing highly accurate temperature distribution control using such a temperature measurement method. The purpose is to provide.

  The present invention is for solving at least one of the above-mentioned objects, and the temperature measurement method in the wafer heat treatment apparatus according to the present invention for achieving the above-described object enables individually controlling the input power. A method for measuring a temperature of a wafer heated by a wafer heat treatment apparatus having an induction heating coil and an induction heating member whose heating region is defined by the induction heating coil, the temperature distribution of the surface of the wafer being measured It is measured by a thermography unit, and an average temperature of the indirect heating region unit in the wafer is calculated based on the measured temperature data.

  Further, in the temperature measurement method having the above-described characteristics, the average temperature is a plurality of points randomly selected from the pixels of the thermography unit, which are determined to measure the temperature of each indirect heating region. The temperature data recorded in the pixels of the first and second pixels are compared, and an average value based on the temperature data excluding the temperature data of the pixels having data indicating the highest temperature and the lowest temperature among the compared temperature data can be obtained.

  If the average temperature is calculated in this way, the selected measurement temperature data contains a singular point (data with extremely high temperature or data with extremely low temperature). In addition, it is possible to accurately derive the average temperature of the indirectly heated region that is the measurement target.

  Further, in the temperature measurement method having the characteristics as described above, the average temperature is a plurality of points randomly selected from the pixels of the thermography unit, which are determined to measure the temperature of each indirect heating region. When the temperature data recorded in the pixel of the pixel is compared with the closest temperature data, the average value based on the temperature data excluding the temperature data of the pixel having a difference equal to or greater than a predetermined threshold as an error range You can also

  If the average temperature is calculated in this way, the average temperature is obtained by excluding the temperature data having a temperature difference that is greater than or equal to the error range compared to the other temperature data, so the number of selected pixels is Even if the amount is small, the average temperature can be accurately derived.

  Further, the temperature control method in the wafer heat treatment apparatus according to the present invention is based on the average temperature derived by the temperature measurement method in the wafer heat treatment apparatus according to any one of the above, and the average temperature of each indirect heating region is calculated. The power input to the induction heating coil for heating each heating region in the induction heating member is adjusted so that the difference is reduced.

  Furthermore, the temperature control method in the wafer heat treatment apparatus according to the present invention is higher than a predetermined threshold value as an allowable value as compared with the average temperature derived by the temperature measurement method in the wafer heat treatment apparatus according to any one of the above. When detecting a pixel group in which a plurality of pixels of the thermography unit having temperature data is detected, the pixel group is recorded as contact data indicating that the heat generating member or the heat transfer member is in contact with the wafer, and the pixel group is detected. The power input to the induction heating coil for induction heating the corresponding heating area may be reduced so as to reduce the temperature of the heating area for heating the indirect heating area.

According to the temperature measurement method in the wafer heat treatment apparatus as described above, the temperature distribution of the wafer to be heat treated can be measured in detail.
Further, according to the temperature control method in the wafer heat treatment apparatus as described above, the temperature distribution of the wafer to be heat treated can be controlled with high accuracy.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to a temperature measurement method and a temperature control method in a wafer heat treatment apparatus of the present invention will be described in detail with reference to the drawings. The following embodiments are some embodiments according to the present invention, and the technical scope of the present invention is not limited only to the following embodiments.

  First, a wafer heat treatment apparatus 10 for carrying out the temperature measurement method and the temperature control method of the present invention will be described with reference to FIG. Note that the configuration of the wafer heat treatment apparatus 10 is merely an example, and even when the configuration other than the main configuration is changed, the implementation of the present invention is not affected.

  A wafer heat treatment apparatus 10 shown in FIG. 1 is a cold wall type heating furnace. The wafer heat treatment apparatus 10 includes a heat treatment furnace 13, a power control unit 32 that supplies electric power to the coil unit 17 provided in the heat treatment furnace 13, a semiconductor wafer, a liquid crystal wafer, and the like disposed in the heat treatment furnace 13. A thermography unit 60 that detects a temperature distribution (hereinafter simply referred to as a wafer 30) is configured as a basis.

The heat treatment furnace 13 includes a casing 12 and a heating / cooling unit 14.
The casing 12 is an outer shell of the heat treatment furnace 13 and constitutes a process chamber 50. The casing 12 according to this embodiment is provided with a viewing window 12a at the top. The observation window 12a is a window for detecting the temperature distribution on the surface of the wafer 30 by a thermography unit 60, which will be described in detail later, and is preferably made of barium fluoride having translucency (infrared transmissivity). The heating / cooling unit 14 is a unit for heating or cooling the wafer 30 to be heat-treated. The heating / cooling unit 14 includes a stage 16 constituting an outer shell, a coil unit 17 disposed inside thereof, a first heat insulating member 20, a heat equalizing member 21, a second heat insulating member 22, and an induction heating member. And the separator 24 and the separator 26.

The stage 16 is preferably formed of a non-conductive heat-resistant member such as ceramic or quartz.
In addition, the coil unit 17 is configured by a tubular member (a hollow member including a rectangular cross section), and includes a plurality of induction heating coils 18 (in the case of the present embodiment) in which a coolant such as cooling water or cooling gas can be inserted. 6 of the induction heating coils 18a to 18f) are preferably arranged close to each other.

  Here, by making the induction heating coil 18 as described above, it is possible to prevent the coil itself from being overheated by the heat of the graphite 24 generated by induction heating, and to supply (provide) the coil to the coil. By cutting or adjusting the electric power, it is possible to play a role as a cooling pipe. The induction heating coil 18 having such a configuration is connected to a power control unit 32 for supplying power to the induction heating coil 18 and controlling the heating state of the graphite 24 (separator 26) and the wafer 30. Has been.

  The overall configuration of the coil unit 17 in the present embodiment may be, for example, a configuration in which a plurality of circular (C-type) coils having different radii are arranged close to each other on a concentric circle (for example, JP 2006-278150 A). : See FIG. The power control unit 32 that supplies electric power to the induction heating coils 18 arranged in this way avoids the influence of mutual induction between the induction heating coils 18 arranged close to each other, and the input power to each induction heating coil 18. For example, the following configuration is preferable.

  That is, this unit is based on a phase detector (not shown), the resonance type inverter 34 (34a to 34f), the forward conversion unit 36, and the power supply unit 38. Here, the phase detector is means for obtaining a phase difference between the current waveforms supplied to the induction heating coils 18 by detecting a zero crossing of the current waveforms supplied to the induction heating coils 18. It is. Further, the resonance type inverter 34 is a series resonance type inverter provided corresponding to each induction heating coil 18 and may be, for example, a single-phase full bridge inverter or a half bridge inverter. The resonant inverter 34 according to the present embodiment can both adjust the power supplied to the induction heating coil 18 and control the phase of the current frequency by changing the duty ratio by controlling the pulse width of the input voltage. To do. The forward conversion unit 36 plays a role of converting an alternating current (for example, a three-phase alternating current) supplied from the power supply unit 38 into a direct current. The power supply unit 38 plays a role of supplying an alternating current to the forward conversion unit 36 connected to each resonance type inverter 34. A smoothing circuit (not shown) is provided between the resonance type inverter 34 and the forward conversion unit 36. Each resonance type inverter 34 is connected to a phase / power regulator 40 that outputs a signal for adjusting the phase of the current waveform and adjusting the power to each resonance type inverter 34.

  By including the power control unit 32 having such a configuration, the phase difference between the currents supplied to the induction heating coils 18 is detected and controlled so that the phase difference becomes zero or a preset phase difference. Can be adjusted. Therefore, it is possible to apply desired power to the induction heating coils 18 arranged close to each other so as to form a circle, and the amount of input power to the induction heating coil 18 can be adjusted. Therefore, it is possible to freely control the heating rate of the graphite 24 that is the induction heating member, that is, the temperature distribution, and the heat treatment of the wafer 30 through the separator 26 and the gas layer 29 can be performed with high accuracy. it can.

  Further, the power control unit 32 according to the present embodiment has a terminal 42 (42a) outside the heat treatment furnace 13 constituting the process chamber 50 as shown in the circuit diagram shown in FIG. 2 (the circuit diagram shown in FIG. 2 is two zones). , 42b) are provided to be grounded. The ground location is in the vicinity of the outside of the heat treatment furnace 13 that is not easily affected by electrical elements such as the resonant capacitors 44 (44a, 44b) and the circuit resistances R (Ra, Rb), and an electrical element is placed between the induction heating coil 18 and the ground. It is desirable that the position is not interposed. By setting it as such a structure, the voltage to ground of the induction heating coil 18 can be lowered. For this reason, by applying helium (He) gas or hydrogen (H) gas, which can reduce the contact resistance between the components, to the atmosphere of the coil chamber 52, the minimum discharge start voltage at which Paschen discharge occurs is lowered. Even in this case, Paschen discharge between the induction heating coils 18 can be prevented.

  Here, in the Paschen discharge, the voltage Vs at which the Paschen discharge is generated is determined by the pressure P of the environment where the electric element is placed and the distance D between the electric elements. For example, when the atmosphere of the coil chamber 52 is He, the minimum discharge start voltage of 156 (V) is obtained when the product P · D of the pressure P and the distance D is 5.3 (Pa · m). By determining the grounding location as described above, the voltage to ground takes into consideration only the voltage between the induction heating coils 18 and can be made lower than the minimum discharge start voltage as described above. Can be prevented. As a specific example, when the voltage between the terminals of the resonance capacitor 44 and the circuit resistance R is 600 V and the voltage between the terminals of the induction heating coil 18 is 100 V, the resonance capacitor 44 and the circuit resistance R are between the ground terminal. , The voltage to ground for the induction heating coil 18 becomes 700V. On the other hand, according to the arrangement of the ground terminal 42 as in the present embodiment, the voltage to ground can be targeted only for the voltage between the terminals of the induction heating coil 18 and is 100V.

  The first heat insulating member 20 is preferably a substance having a small heat capacity, and examples thereof include a polyimide film, specifically Kapton (Toray DuPont). The soaking member 21 may be a member having a high thermal conductivity and a low heat capacity. An example is silicon.

  The second heat insulating member 22 may have a large heat capacity, but may have a high heat resistance temperature, and may be a material having a small thermal expansion, such as quartz. The reason why the heat insulating member is provided with quartz and kapton and the heat equalizing member 21 is disposed between them is as follows.

  That is, Kapton can reduce the heat capacity, but the heat-resistant temperature is as low as about 400 ° C. In contrast, quartz has a heat capacity higher than that of Kapton, but has a high heat resistance temperature, and there is no risk of deterioration even when it is in close contact with graphite 24 as a heat source. Quartz is a substance with relatively little thermal expansion. However, when an induction heating coil 18 as a cooling pipe is brought into close contact with one main surface and a graphite 24 as a heat source is brought into close contact with the other main surface, both main surfaces. An extreme temperature difference is given between them, and a large warp occurs in the quartz as the second heat insulating member 22. For this reason, the first heat insulating member 20 having a small heat capacity, that is, Kapton is disposed as a temperature relaxing member between the quartz as the second heat insulating member 22 and the induction heating coil 18.

  And it becomes possible to eliminate the temperature unevenness at the time of cooling based on the arrangement form of induction heating coil 18 by arranging soaking member 21 between the 1st heat insulation member 20 and the 2nd heat insulation member 22. In addition, the temperature equalization at the time of cooling the wafer 30 is facilitated. Further, the heat from the graphite 24 transmitted to the first heat insulating member 20 through the second heat insulating member 22 is diffused by the heat equalizing member 21. Thereby, there is no possibility that the heat transmitted to the first heat insulating member 20 is locally increased, and the heat transmitted from the second heat insulating member 22 to the first heat insulating member 20 is spread over the entire range. 1 heat insulating member 20 can be contained within the heat resistant temperature range. Therefore, partial deterioration of the first heat insulating member 20 can be prevented.

  Further, by adopting the arrangement configuration as described above, the heat transfer between the quartz and the induction heating coil 18 is delayed, and it is possible to alleviate the warp generated in the quartz. Further, as shown in FIG. 3, the quartz according to the present embodiment is divided into a plurality of parts in each of the radial direction and the circumferential direction. By setting it as such a structure, the curvature generate | occur | produced in quartz will arise in an individual unit, and the big curvature as the whole quartz can be suppressed. Further, by dividing in advance, it is possible to prevent quartz from being damaged due to the effect of thermal expansion.

  The graphite 24 serves as a heat medium when the wafer 30 is heated and cooled. For example, when the wafer 30 is heated, it is heated as an induction heating member by the action of magnetic flux (eddy current) generated by the electric power supplied to the induction heating coil 18 to generate heat. On the other hand, when the wafer 30 is cooled, the wafer 30 is cooled by the action of a coolant poured into the induction heating coil 18 and functions as a heat absorbing member that absorbs radiant heat from the heated wafer 30 and also transfers heat. It will also work as a medium. In addition, heat exchange between the graphite 24 and the refrigerant poured into the induction heating coil 18 is performed by a component (for example, copper) of the induction heating coil 18, a component (for example, Kapton) of the first heat insulating member 20, or the like. The heat member 21 and the second heat insulating member 22 are configured through heat transfer of members such as constituent members (for example, quartz).

  As the type of the graphite 24, it is desirable to employ a graphite sheet that can be compressed in response to thermal expansion of other components. With this configuration, it is not necessary to consider the expansion coefficient of the graphite 24, and the graphite 24 can be used as a buffer member against thermal expansion of other components.

  Further, the graphite 24 according to the present embodiment is divided into a plurality of pieces in the radial direction as shown in FIG. According to such a configuration of the graphite 24, heat transfer generated between adjacent heating zones can be suppressed, and heating unevenness caused by deviation of the arrangement position of the graphite 24 and the induction heating coil 18 can be prevented. Can be reduced. For this reason, even if there is no rotating structure between the graphite 24 and the induction heating coil 18, it is possible to reduce the heating unevenness of the graphite 18. Therefore, it is possible to perform the uniform heating of the entire graphite 24 and the temperature control in units of heating zones with higher accuracy with a simple structure. Further, the heating range (heating zone) by each induction heating coil 18 is also clarified.

  The separator 26 only needs to have the following elements. That is, it has translucency (infrared transmissivity) to transmit radiant heat from graphite 24 as a heat source, has heat resistance equal to or higher than the heat treatment temperature, has a low coefficient of linear expansion, and a low thermal expansion. good. Specifically, a plate member made of quartz is desirable. In consideration of the heat capacity, it is desirable to make the separator plate 26 as thin as possible. However, when the separator plate 26 is thinned, there is an increased possibility of warping due to the effects of thermal expansion and the influence of its own weight, resulting in damage. For this reason, in this embodiment, the pressure inside the process chamber 50 is made higher than the pressure inside the coil chamber 52, and the separator 26 is brought into close contact with the graphite 24, thereby suppressing the warpage of the separator 26. Further, by increasing the atmospheric pressure inside the process chamber 50, it is possible to prevent contamination inside the coil chamber 52 from entering the process chamber 50. In the present embodiment, the inside of the coil chamber 52 is a helium (He) gas atmosphere. The helium gas can reduce the contact resistance between the components arranged inside the coil chamber 52 and can improve the efficiency of heat transfer between the components.

  And in the induction heating apparatus 10 which concerns on this embodiment, when mounting the wafer 30, the structure which makes the separator plate 26 and the wafer 30 adjoin and interpose the gas layer 29 between both is taken. Yes.

  Specifically, a ring-shaped member that supports the outer peripheral portion of the wafer 30 is arranged on the upper surface of the separator plate 26, that is, the surface facing the wafer 30, or block members are interspersed. Just do it. With such a configuration, the area where the wafer 30 is supported (contact area) is very small with respect to the ratio of the wafer 30 in the processing surface. For this reason, the difference in thermal conductivity at the contact point between the wafer 30 and the susceptor 28 can be almost ignored.

  Here, the gas layer 29 generally has a lower heat transfer efficiency than a layer composed of a liquid or a solid. For this reason, when heat transfer is used for heating the wafer 30, it is general that the heat source and the wafer 30 are in close contact with each other. In the present invention, quartz as the separator 26 and the gas layer 29 are interposed between the graphite 24 as the heat generation source and the wafer 30, and the area occupied by the gas layer 29 in contact with the wafer 30 is in contact with the wafer 30. By making it larger than the area occupied by the susceptor 28, variations in thermal conductivity are suppressed, and the temperature distribution of the wafer 30 is made uniform. Note that the gas layer 29 in the present embodiment includes a process gas such as nitrogen (N), helium (He), and argon (Ar) in addition to the atmosphere diluted by evacuation.

  The appropriate value of the thickness d of the gas layer 29 interposed between the separator 26 and the wafer 30 is influenced by the concentration and physical properties of the gas constituting the gas layer 29, but when the wafer 30 is heated or What is necessary is just to set it as the distance which can perform heat exchange between the separator 26 and the wafer 30 by using the said gas layer 29 as a heat medium at the time of cooling. However, it is desirable that the value of the thickness d of the gas layer 29 be as small as possible when performing the rapid temperature increase / decrease control. This is because by reducing the thickness d of the gas layer 29, it is possible to increase the responsiveness of heat exchange between the wafer 30 and the separator plate 26. From such a viewpoint, in the wafer heat treatment apparatus 10 used in this embodiment, it is desirable that the thickness is, for example, about 150 μm.

  The heat treatment and cooling treatment of the wafer 30 in the wafer heat treatment apparatus 10 configured as described above are performed by both heat transfer using the gas layer 29 as a heat medium and absorption or emission of radiation. For this reason, it is possible to give a temperature increase / decrease rate of several tens of degrees Celsius / S or more to a wafer 30 having infrared transparency (for example, a semiconductor wafer having a heating temperature of 500 ° C. or lower) 30 that is considered to have poor heating efficiency. Further, since the temperature distribution of the gas layer 29 is equalized, the temperature distribution of the wafer 30 is improved, and the local overshoot in the temperature control can be controlled to 10 ° C. or less.

  The thermography unit 60 is a unit that detects infrared rays radiated from a measurement object, converts the detected energy data into an apparent temperature (temperature data), and displays it as image data indicating a temperature distribution. For this reason, the temperature distribution on the surface of the measurement object can be displayed as visualization information, and a wide range of temperature distributions can be relatively compared. Further, since infrared rays radiated from the measurement object are detected, temperature measurement can be performed in a non-contact manner, and temperature measurement is possible even for an object whose temperature changes rapidly.

  The principle of thermography is generally as shown in FIG. First, the infrared energy radiated from the measurement symmetry object passes through the atmosphere (including process gas in the case of the embodiment), is taken in from the condenser lens, and is collected by the detector. The condensed infrared light is converted into an electric signal through a detector (electronic operation) and amplified through an amplifier. The amplified electric signal is converted into digital data by an A / D converter, and image processing such as calculation and correction is performed via a calculation unit such as a CPU or a personal computer, and a temperature distribution is displayed on a display unit such as a monitor (not shown). Is displayed as an image (see FIG. 6).

  Here, a germanium lens that transmits infrared rays and does not transmit visible light is used as the condenser lens. As the detector, either a quantum type that detects a change due to a photoelectric effect or a thermal type that detects a temperature rise due to infrared radiation can be adopted. For example, a microbolometer can be cited as a thermal detector.

  The detection of the temperature distribution by the thermography unit 60 depends on the number of pixels of the detection element in the detector, and the detected temperature can be known for each pixel. As shown in FIG. 7, the number of pixels indicates the number of pixels existing on a matrix represented by vertical pixels and horizontal pixels. The detected temperature, that is, the difference in the amount of infrared energy is represented by the color for each gradation determined by the data depth determined for each pixel. For example, when the data depth is 12 bits, one pixel has a data amount for 4096 gradations, and when the temperature change for each gradation is 0.1 ° C., the change for 409.6 ° C. Can show.

  The thermography unit 60 according to the present embodiment includes a calculation unit 62 provided outside, and generates a temperature distribution image and can also generate a signal for the phase / power adjuster 40.

  As specific processing, first, based on the data output from the thermography unit 60, the temperature distribution of the wafer 30 is detected by the calculation means 62. Next, based on the detected temperature distribution data, a temperature difference for each heating zone (indirect heating region) of the wafer 30 assigned to each induction heating coil 18 and an error with respect to the set temperature are calculated.

  In this embodiment, when calculating the temperature difference for each indirect heating region or an error with respect to the set temperature, the pixel data defined as pixels for detecting the temperature of each indirect heating region is cut out, and the pixel having this temperature data A plurality of random images are randomly selected from the image data, and an average temperature is obtained from the temperature data (infrared energy amount) recorded in the selected pixels, and this is used as the representative temperature of each indirect heating region. By calculating the temperature difference between each indirect heating area and the error for the set temperature in this way, the amount of data required for the calculation can be reduced, and high-speed temperature detection processing and temperature distribution control can be performed. Because it becomes.

  Here, the average temperature, that is, the representative temperature in the indirect heating region, when comparing the temperature data recorded in a plurality of selected pixels, the pixel having the temperature data indicating the highest temperature and the temperature indicating the lowest temperature. The average value of the remaining temperature data excluding the temperature data of the pixels having data may be used. If the average temperature is calculated in this way, the selected temperature measurement data has a singular point (a point having temperature data indicating that the temperature is extremely high, or a temperature indicating that the temperature is extremely low). This is because the average temperature of the indirect heating region that is the detection target can be derived with high accuracy even when the point having data is included.

  Further, the average temperature may be as follows. That is, the temperature data recorded in a plurality of selected pixels is compared, and when compared with the closest temperature data, temperature data excluding the temperature data of pixels having a difference equal to or greater than a predetermined threshold as an error range The average value based on Here, the threshold value defined as the error range depends on the heat treatment accuracy required for the wafer to be manufactured, but since the average temperature is derived in units of indirect heating regions, it should be less than the allowable temperature difference required for the entire wafer. For example, it may be less than a few degrees. If the average temperature is calculated in this manner, the average temperature can be accurately derived even when the number of selected pixels is small.

  Next, a signal for determining the duty ratio by calculating whether the power supplied to each induction heating coil 18 should be increased, decreased, or how much power is required to compensate for the detected temperature difference and error. To the phase / power regulator 40. With such a configuration, feedback control based on the detected temperature of the wafer 30 is possible.

  Here, based on the detected temperature of the wafer 30 detected as described above, the power supplied to the induction heating coil 18 should be increased, decreased, or the required power value is calculated. When performing the above, it is necessary to perform control in consideration of the environmental temperature, such as the influence of the cooling action by the refrigerant poured into the induction heating coil 18. Therefore, as a control method, PID control including a proportional gain Kp, an integral gain Ki, and a differential gain Kd is adopted in the control system, a desired temperature profile is given to the normal temperature wafer 30, and a rapid temperature change is performed. Even if the above occurs, it is desirable to make the temperature distribution approach or reach the target value correspondingly.

  Specifically, first, a temperature command value up to a target value for heating the wafer 30 is given in time series. Then, the set temperature of the separator 26 (substance that substantially exchanges heat with the wafer 30), which is an input value for filling the deviation between the command value at a certain time and the temperature of the wafer 30, is set to the proportional gain Kp. Calculate based on

  At this time, when the cooling action by the refrigerant or the like occurs with respect to the environmental temperature, that is, when the environmental temperature changes, the command value may not be reached at the set temperature calculated by the proportional gain Kp. That is, the temperature of the wafer 30 heated at the set temperature deviates from the temperature given as the command value. A deviation (residual deviation) caused by such a divergence is compensated by a set temperature correction value calculated using the integral gain Ki, so that the command value and the temperature of the wafer 30 coincide.

  However, since the so-called I operation based on the integration time does not work unless a predetermined time elapses after the temperature changes, when the temperature deviates from the command value, the temperature is returned to the command value. It takes time. Therefore, when a sudden temperature change occurs, an input value proportional to the change rate of the deviation from the command value is calculated by the differential gain Kd, and this is given as a correction value to cope with the sudden change. Then, the command value and the temperature of the wafer 30 are matched.

  The temperature control of the wafer 30 is performed by repeatedly feeding back the temperature detection of the wafer 30, the calculation of the set temperature of the separator 26, and the power control for raising the temperature of the separator 26 to the set temperature. Is made.

  By performing temperature measurement and temperature control in this manner, total temperature unevenness in a predetermined indirect heating region is reduced. For such temperature measurement and temperature control, for example, when temperature measurement is performed at only one point in a certain indirect heating region, if only the temperature at that point is extremely low (or high), that is the representative temperature. Since the temperature is controlled, the indirect heating region is excessively heated (or cooled), so that the temperature of the entire indirect heating region becomes higher (or lower).

  Note that when the wafer 30 is cooled using the wafer heat treatment apparatus 10, rapid cooling is performed using a cooling action by a refrigerant. However, when overcooling occurs, cooling is performed by induction heating. The rate can be adjusted. Even in such a temperature lowering process, it is possible to give a desired temperature gradient to the wafer 30 by executing the feedback control as described above.

  Further, in the actual temperature raising / lowering process, the shape and size of the induction heating coil 18 and the influence of radiant heat, etc., cause local high temperature portions and low temperature portions in the graphite 24, which also causes the separator plate 26. Similar temperature gradients may occur. For this reason, in the induction heating apparatus 10 having the above-described configuration, the amount of power input to each induction heating coil 18 is finely adjusted, the temperature distribution on the main surface of the graphite 24 is equalized, and the temperature rise and fall control of the entire separator 26 is performed. Will be performed.

  Further, when temperature irregularity or the like occurs in the wafer 30, the wafer 30 bends, and the wafer 30 is a heat generating member graphite 24 (in the apparatus shown in FIG. 1, the heat transfer member is in contact with the graphite 24). May come into contact with the plate 26). In such a case, a local high temperature portion appears in a portion in contact with the graphite 24 or the separator plate 26. When the calculation means 62 detects a pixel group having such temperature data indicating a local high temperature, it determines that the wafer 30 is in contact with the graphite 24 and the like, and records this as contact data in the heat treatment history of the wafer 30. To do. This is because by leaving such a record, it is possible to determine whether or not the wafer 30 can be used according to the history when the wafer 30 is transferred to a subsequent process. In addition, regarding the determination of a local high temperature part, it shall say the location which became higher than the threshold value predetermined as an allowable value from the average temperature of an indirect heating area | region. Further, the threshold value predetermined as the allowable value may be a temperature difference desired for the heat treatment of the wafer 30.

  Further, when the above-described local high temperature portion is generated on the wafer 30, the induction heating coil 18 is charged so as to lower the temperature of the heating region of the graphite 24 that heats the indirect heating region including the high temperature portion. Reduce power. By performing such control, the temperature distribution of the wafer 30 to be heat-treated can be controlled with high accuracy.

It is a figure which shows the structure of the wafer heat processing apparatus for enforcing the temperature measuring method which concerns on invention, and a temperature control method. It is an equivalent circuit diagram which shows the position of the ground terminal provided in the power control unit. It is a top view which shows the structure of a 2nd heat insulation member. It is a top view which shows the structure of a graphite. It is a block diagram for demonstrating the principle of thermography. It is a figure which shows the example of the temperature distribution image detected by the thermography unit. It is a figure explaining the pixel structure of the detection element of the detector in a thermography unit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ......... Wafer heat treatment apparatus, 12 .... Case, 13 ..... Heat treatment furnace, 14 ..... Heating / cooling unit, 16 ..... Stage, 18 (18a-18f) ...... Induction heating coil, 20 ......... first heat insulating member, 21 ......... soaking member, 22 ......... second heat insulating member, 24 ......... graphite, 26 ......... separator, 28 ......... susceptor, 29 ......... Gas layer, 30 ......... Wafer, 32 ......... Power control unit, 34 (34a to 34f) ......... Resonant inverter, 36 ......... Forward conversion unit, 38 ......... Power supply unit, 40 ...... Phase Controller, 42 (42a, 42b) ......... ground terminal, 44 (44a-44f) ......... resonance capacitor, 50 ......... process chamber, 52 ......... coil chamber, 60 ...... thermographic unit, 62 ... ...... Calculation means.

Claims (5)

A method for measuring the temperature of a wafer heated by a wafer heat treatment apparatus having an induction heating coil that can individually control input power and an induction heating member whose heating region is defined by the induction heating coil. ,
Measure the temperature distribution of the surface of the wafer with a thermography unit,
A temperature measurement method in a wafer heat treatment apparatus, wherein an average temperature of an indirect heating region unit in the wafer is calculated based on measured temperature data.   The average temperature was determined by measuring the temperature of each indirect heating region, and the temperature data recorded in a plurality of pixels randomly selected from the pixels of the thermography unit were compared and compared. 2. The temperature measurement method in a wafer heat treatment apparatus according to claim 1, wherein the temperature measurement method is an average value based on temperature data excluding temperature data of pixels having data indicating the highest temperature and the lowest temperature in the temperature data. .   The average temperature is determined to measure the temperature of each of the indirect heating regions, and the temperature data recorded in a plurality of pixels randomly selected from the pixels of the thermography unit are compared and the closest 2. The wafer heat treatment apparatus according to claim 1, wherein the wafer heat treatment apparatus is an average value based on temperature data excluding temperature data of pixels having a difference equal to or larger than a predetermined threshold as an error range when compared with temperature data. Temperature measurement method. Based on the average temperature derived by the temperature measurement method in the wafer heat treatment apparatus according to any one of claims 1 to 3,
Temperature control in a wafer heat treatment apparatus, wherein power supplied to the induction heating coil for heating each heating region in the induction heating member is adjusted so that a difference in the average temperature for each indirect heating region is small Method. A pixel of a thermography unit having temperature data higher than a predetermined threshold as an allowable value compared to the average temperature derived by the temperature measuring method in the wafer heat treatment apparatus according to any one of claims 1 to 3. When detecting a pixel group in which a plurality of sets are detected, it is recorded as contact data indicating that the heat generating member or the heat transfer member is in contact with the wafer, and
The wafer is characterized in that the input power to the induction heating coil for induction heating the corresponding heating area is reduced so as to reduce the temperature of the heating area for heating the indirect heating area as the detection target of the pixel group. A temperature control method in a heat treatment apparatus.

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